Electronic Devices and Circuits problems
- 1. A silicon (PN) junction at a temperature of 20°C has a reverse saturation current of 10 pico Ampere. The reverse saturation current at 40°C for the same bias is approximately.
Options- A. 30 pA
- B. 40 pA
- C. 50 pA
- D. 60 pA Discuss
Correct Answer: 40 pA
Explanation:
By increasing of temperature by 10°C, Io become double so by increasing temperature 20°C, Io become 4 time than initial value... and it is 40 PA.
- 2. Ferrite have
Options- A. low copper loss
- B. low eddy current loss
- C. low resistivity
- D. higher specific gravity compared to iron Discuss
Correct Answer: low resistivity
Explanation:
Ferrite is a low density material of composition with Fe2O3 x O, where x is a bivalent metal, such as Cobart, Ni, Mn. These magnetic materials having very low loss of current and used in high frequency circuit.
- 3. A particular green LED emits light of wavelength 5490, Å, the energy bandgap of the semiconductor material used there is .. h = 6.6 x 10-34 J sec.
Options- A. 2.26 eV
- B. 1.98 eV
- C. 1.17 eV
- D. 0.74 eV Discuss
Correct Answer: 2.26 eV
Explanation:
From Plank equation 
joule
joule
to convert it into electron volt it will be divided by 1.6 x 10-19.
- 4. The normal operation of JFET is
Options- A. constant voltage region
- B. constant current region
- C. both constant voltage and constant current regions
- D. either constant voltage or constant current region Discuss
Correct Answer: constant current region
Explanation:
In major portion of drain characteristics ID is constant.
- 5. In a degenerate n type semiconductor material, the Fermi level,
Options- A. is in valence band
- B. is in conduction band
- C. is at the centre in between valence and conduction bands
- D. is very near valence band Discuss
Correct Answer: is in conduction band
Explanation:
This is due to high level of doping.
- 6. The power dissipation in a transistor is the product of
Options- A. emitter current and emitter to base voltage
- B. emitter current and collector to emitter voltage
- C. collector current and collector to emitter voltage
- D. none of the above Discuss
Correct Answer: collector current and collector to emitter voltage
Explanation:
Maximum power dissipation occurs at collector junction.
- 7. In an n-p-n transistor biased for operation in forward active region
Options- A. emitter is positive with respect to base
- B. collector is positive with respect to base
- C. base is positive with respect to emitter and collector is positive with respect to base
- D. none of the above Discuss
Correct Answer: base is positive with respect to emitter and collector is positive with respect to base
Explanation:
In forward active mode emitter base junction is forward biased and base collector junction is reverse biased.
- 8. In a zener diode
Options- A. the forward current is very high
- B. sharp breakdown occurs at a certain reverse voltage
- C. the ratio v-i can be negative
- D. there are two p-n junctions Discuss
Correct Answer: sharp breakdown occurs at a certain reverse voltage
Explanation:
When reverse voltage equals breakdown value it starts conducting and voltage does not increase further.
- 9. As compared to an ordinary semiconductor diode, a Schottky diode
Options- A. has lower cut in voltage
- B. has higher cut in voltage
- C. lower reverse saturation current
- D. both (b) and (c) Discuss
Correct Answer: has lower cut in voltage
Explanation:
Cut in voltage in Schottky diode is about 0.3 V as compared to 0.7 V in ordinary semiconductor diode.
- 10. A periodic voltage has following value for equal time intervals changing suddenly from one value to next... 0, 5, 10, 20, 50, 60, 50, 20, 10, 5, 0, -5, -10 etc. Then rms value of the waveform is
Options- A. 31 V
- B. 32 V
- C. insufficient data
- D. none of these Discuss
Correct Answer: 31 V
Explanation:
RMS value = 965 = 31.064 Volt.
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